Have your say & ask the experts

They'll have to come out with a new screen technology which is actually watchable in HD first !

Seriously though, there is no reason to have HD on every channel. Don't forget that a great majority of the channels we have at the moment show SD originated material, and some of which was originally 4:3. Also, there are some of them who still insist on showing SD 16:9 originated material either in 14:9 letterbox or worse still, 4:3 centre cut out. From a financial point of view, there is absolutely no point in any broadcaster going to the expense of up-resing this material to HD - and don't forget, even if they did, it would still not be HD.

After all the compression and signal paths most broadcast signals go through,the picture you'd get from a decent SD signal, up-ressed by your TV would probably not look that different to that from an upressed SD to HD master which would have to be compressed even further to get it down the available bandwidth and going through the same signal paths.

The amount of HD channels will increase (we now master most of our work onto HD) as more production companies realise they have to future proof their assets, and also as more channels for HD material become available, but I don't think you'll be seeing old series of Top Gear on DAVE on an HD channel any day soon.

Rob 

robjcooper:

They'll have to come out with a new screen technology which is actually watchable in HD first !

Not sure what you mean there, my screen is eminently watchable in HD.

Seriously though, there is no reason to have HD on every channel. Don't forget that a great majority of the channels we have at the moment show SD originated material, and some of which was originally 4:3. Also, there are some of them who still insist on showing SD 16:9 originated material either in 14:9 letterbox or worse still, 4:3 centre cut out.

Hello Dave!

Why do they do that though? Why not just transmit it in the format it's given to them in, unless the BBC butcher QI themselves before handing it over to Dave?

We are still waiting for proper standard definition on all channels let alone high definition. The showcase high definition channels may look good now especially in comparison to the sub-par standard definition channels. They are currently like shop window displays selling high definition receivers and subscriptions, I hope high definition takes along time to become the norm as when it does picture quality may plumet. With lower bit-rates you get a more passable/acceptable picture quality dropping the resolution rather than just lowering the bit-rate, so despite improved compression systems it could end up looking even lower quality than current standard definition if every channels wants to claim 1080i resolution. The goverment needs to set out minimum standards for picture quality not promote higher resolution. With the main standard definition terrestial digital channels the goverment already sets out quality minimums. For other terrestial channels and all satellite channels it is the wild west. Resolution is pretty meaningless unless you also know the amount of pre-smoothing and bit-rate.

Take current standard definition pal. In theory it is can be as high as 576 lines x 720 samples, progressive scan with 4:4:4 colour encoding. In practice DVD is the highest quality standard definition source and it is stored interlaced and heavily filtered, vertically to reduce interlace line twitter, horizontally to reduce bit-rates, and colour is stored subsampled at half vertical and horizontal resolution. Bit rates for DVDs are adaptive and typically average around 4000kbps to 5000kbps with peaks of 7000kbps to 8000kbps for action scenes (the theoretical maximum is  9800kbps but that is without any audio).

Standard definition satellite is anywhere from dvd`s full-D1 resolution 576ix720, to cropped-D1 576ix704, to sub-sampled D1 576ix544, to even lower 576ix528, 576ix480, 576ix352 and 288ix352 resolutions. A 16:9 image may also be letterboxed rather than anamorphic for even lower resolution. As with DVD the image is also filtered first to reduce interlaced line flicker and bit-rates, so these resolutions are even softer looking. Bit-rates for current standard definition satellite tv are also lower than dvd, 4406kbps for each of BBC 1 NI and BBC 2 NI, while if you pay extra for SKY you are looking at enjoying bit-rates as low as 2433kbps for Sky One their flagship general entertainment channel, and if you rely on free tv you can get even lower quality like Zone Horror +1 at 1324kbps.

High definition satellite 1080i should be 14-16000kbps according to the EBU. BBC 1 HD was originally at 20000kbps but is now down to 9721kbps (while still transmitting on other satellites to European networks at 16000kbps). Sky One HD is at 14844kbps which begs the question why is Sky One SD at 2433kbps.

I'm not a great fan of LCD screens, finding every one of them I've seen has some kind of artifact which makes them unwatchable for me - I spend my working day in front of a 32" Sony HiDef Grade 1 CRT Broadcast Monitor so I've been spoilt - at the moment i'm in an Avid DS watching 'Life' straight from the HDCam SR master - and it looks glorious. I loved the Pioneer Kuro's though, and if I'd had £2500 i'd have bought one the first time I saw one, but 3 kids and a house mid-restoration ruled that out !  2 of our senior engineers who've lined up more monitors than I care to think about, both have CRTs and one of them still prefers to watch a (very large) 4:3 Sony Trinitron.

A lot of the reasons for the mish mash of ratios is to do with satisfying regulations regarding viewers who still have 4:3 televisions and receive analogue pictures being able to read the captions and text. This is why when we're making programmes we have to stick to very rigid caption safe areas. For instance, the BBC insist on all captions being within a 4:3 caption safe area on a 16:9 image which is 60% width and 80% height - next time you're watching a programme on BBC see how centralised the name supers and captions are. The transmission of a 14:9 letterbox image gives us a little more leeway on our 16:9 master (68%width and 80% height). But most of the Letterboxed and 4:3 shows on certain channels are transmitted like that so that everyone no matter what receiver they have can read the captions and the broadcaster doesn't have to worry about simulcasting various different ratios on various platforms! Also, not all broadcasters buy their material from the originators and as such may not have access to the 16:9 masters - we still make pan and scan 4:3 versions of most programmes for international sales. So if Channel Y does a deal with Distributor X it may only be for those none 16:9 versions.

At least QI is transmitted in 14:9 letterbox and not centre cut 4:3 ! 

 "You're my Fry now !"

Rob 

P.S. no standard definition broadcast tape format allows the recording of a 4:4:4 or a progressive scan signal - every broadcast SD format is interlaced . Broadcast 601 spec is for a 4:2:2 signal. DVD is a high quality non broadcast home format using quite large amounts of MPEG compression and bears no relation to the D1 format which was uncompressed 8bit 4:2:2. It's successor was Digital Betacam which was a 10bit 4:2:2 format with mild 2:1 compression which is the standard delivery format for all broadcasters (the BBC toyed with D5 which was an uncompressed 10bit 4:2:2 format but the VTR's were a pain and it wasn't adopted by anyone - The BBC moved to Sony's far superior Digital Betacam. In the HD world, HDCam SR however can record a 4:4:4 1080psf signal and now feature films are being recorded onto this format. However most broadcasters will accept 4:2:2 HDCam or HDCam SR masters.

robjcooper:

P.S. no standard definition broadcast tape format allows the recording of a 4:4:4 or a progressive scan signal - every broadcast SD format is interlaced . Broadcast 601 spec is for a 4:2:2 signal. DVD is a high quality non broadcast home format using quite large amounts of MPEG compression and bears no relation to the D1 format which was uncompressed 8bit 4:2:2. It's successor was Digital Betacam which was a 10bit 4:2:2 format with mild 2:1 compression which is the standard delivery format for all broadcasters (the BBC toyed with D5 which was an uncompressed 10bit 4:2:2 format but the VTR's were a pain and it wasn't adopted by anyone - The BBC moved to Sony's far superior Digital Betacam. In the HD world, HDCam SR however can record a 4:4:4 1080psf signal and now feature films are being recorded onto this format. However most broadcasters will accept 4:2:2 HDCam or HDCam SR masters.

For video cameras interlaced. But what about for films. The old Palplus system had a film mode and colorplus for progressive display and reduced color noise. Like current widescreen digital tv it also maintained the 576 lines of resolution with widescreen material. Its main disadvantage was it required a 100Hz display. Sadly it never took off, as the improved picture quality was not hyped enough. Likewise super-bit dvds have less horizontal filtering for better picture quality but never took the market by storm. Dvds despite being interlaced could be mastered for progressive displays, so having alot less filtering - smoothing of the image.

People claim a massive improvement in picture quality with high definition but I think alot of this is down to current standard definition being low quality, its good enough, rather than as good as it could be. Standard definition setups can also be very poor, due to poor de-interlacers and scalers or using poorly setup component vidieo or the terrible scart composite video. High definition digital is alot more plug and play.  

My worry is that high definition will also end up being good enough, bit-rate starved. It amazes me that sky one standard definition is so low bit-rate, since it is simultaneous broadcast in high definition it is not a limitation of the source material. Free standard definition satellite chanels can be so low bit-rate it is suprising they are watchable.

Film is recorded onto broadcast specification tape interlaced. Each film frame is captured by the telecine, stored in a buffer and recorded as half the single frame resolution on consecutive fields. Odd lines of the frame in the buffer are recorded on field one and even lines are recorded on field 2. Play it back and our persistence of vision gives us images like film - Field doubling of video images (i.e. using a single field of a frame only but repeated twice gives video the look of film, although losing half the vertical resolution in the process - watch some old Top Gear shows and look at the jagged lines on any diagonal - a sure sign of 'Film Effect' ) Video recordings have temporally different images on each field, as they record a different image although of half the frame vertical resolution, 50 times a second - one of the reasons sport has a sharper look on videotape and apparently on 1080i.

PalPlus was an analogue transmission format which was a first attempt at transmitting 16:9 images (which Channel 4 dabbled with) but was replaced by the appearance of digital anamorphic 16:9, which has the full 576 horizontal lines but 'unstretches' the image from 720 horizontal pixels to 1024. And although SCART had composite video on one of its pins, it also allowed the use of the much higher quality S-Video and even better still RGB (although not at the same time) if your equipment was able to accept these signals.  

Hi-Definition is a massive improvement over SD when it leaves us and before the broadcasters crunch it down so that they can also send 52 shopping channels and TV bingo down the limited bandwidth available. I couldn't agree with you more that the broadcasters appear to be simply going as low, quality wise, and high compression rates wise, as they can with HD images (as well as persisting with transmitting the utter garbage which the deplorable Simon Cowell seems to puke forth). I would still argue that a lot of the problems with HD are also due to the limitations of the LCD screens people are watching stuff on - throwing the massive amount of processing at an image as most LCD's do to 'improve' the image just proves to me that they are just not good enough. As I've said before, if the manufacturers could have made a bigger screen, smaller cabinet HD CRT for the same money they would not have bothered with LCD at all.

I look forward to when HD is broadcast at 1920/1080 50fps.

BBCHD has taken a big hit in picture quality recently, although the problems with motion smearing/tracking have always been there, why do we still use 25fps anyway? and how much of poor motion is down to the frame rate the footage was recorded in?

knightout:

We are still waiting for proper standard definition on all channels let alone high definition. The showcase high definition channels may look good now especially in comparison to the sub-par standard definition channels. They are currently like shop window displays selling high definition receivers and subscriptions, I hope high definition takes along time to become the norm as when it does picture quality may plumet. With lower bit-rates you get a more passable/acceptable picture quality dropping the resolution rather than just lowering the bit-rate, so despite improved compression systems it could end up looking even lower quality than current standard definition if every channels wants to claim 1080i resolution. The goverment needs to set out minimum standards for picture quality not promote higher resolution. With the main standard definition terrestial digital channels the goverment already sets out quality minimums. For other terrestial channels and all satellite channels it is the wild west. Resolution is pretty meaningless unless you also know the amount of pre-smoothing and bit-rate.

Take current standard definition pal. In theory it is can be as high as 576 lines x 720 samples, progressive scan with 4:4:4 colour encoding. In practice DVD is the highest quality standard definition source and it is stored interlaced and heavily filtered, vertically to reduce interlace line twitter, horizontally to reduce bit-rates, and colour is stored subsampled at half vertical and horizontal resolution. Bit rates for DVDs are adaptive and typically average around 4000kbps to 5000kbps with peaks of 7000kbps to 8000kbps for action scenes (the theoretical maximum is  9800kbps but that is without any audio).

Standard definition satellite is anywhere from dvd`s full-D1 resolution 576ix720, to cropped-D1 576ix704, to sub-sampled D1 576ix544, to even lower 576ix528, 576ix480, 576ix352 and 288ix352 resolutions. A 16:9 image may also be letterboxed rather than anamorphic for even lower resolution. As with DVD the image is also filtered first to reduce interlaced line flicker and bit-rates, so these resolutions are even softer looking. Bit-rates for current standard definition satellite tv are also lower than dvd, 4406kbps for each of BBC 1 NI and BBC 2 NI, while if you pay extra for SKY you are looking at enjoying bit-rates as low as 2433kbps for Sky One their flagship general entertainment channel, and if you rely on free tv you can get even lower quality like Zone Horror +1 at 1324kbps.

High definition satellite 1080i should be 14-16000kbps according to the EBU. BBC 1 HD was originally at 20000kbps but is now down to 9721kbps (while still transmitting on other satellites to European networks at 16000kbps). Sky One HD is at 14844kbps which begs the question why is Sky One SD at 2433kbps.

well it most be HD (HIGHLY DISTANT) in the future!!!